Pump for molten salts and metals

ABSTRACT

A pump comprising a refractory body portion of oblate spheroidal configuration having apertures in the top and bottom thereof is provided with refractory covers for said apertures which covers are held securely in said apertures by upper and lower metal plates, respectively, the upper plate forming the base of a vertical housing for the pump impeller shaft and the lower plate being resiliently mounted for vertical movement relative to said upper plate to compensate for thermo-expansion and contraction of the pump elements.

United States Patent 1 Anderson et al.

[ PUMP FOR MOLTEN SALTS AND METALS [75] Inventors: Loren E. Anderson, Las Vegas; Roy

E. Adams; Gordon D. Weese, both of Henderson, all of Nev.

[73] Assignee: NL Industries, Inc.', New York, NY.

[22] Filed: Feb. 22, 1972 [21] Appl. No.: 227,767

[52] US. Cl 415/196, 415/200, 415/219 C, 204/245, 415/212 [51] Int. Cl. F04d 7/02, F04d 7/06 [58] Field of Search 415/219 C, 197, 196,

[56] References Cited UNITED STATES PATENTS 1,727,703 9/1929 Hause et al. 415/196 2,528,210 10/1950 Stewart 2,347,386 4/1944 Adams 3,255,702 6/1966 Gehrm...... 3,459,133 8/1969 Scheffler 415/196 Dec.4, 1973 3,532,445 l0/1970 Scheffler et a] 415/214 3,612,715 10/1971 Yedidiah 415/214 FOREIGN PATENTS OR APPLICATIONS 1,270,174 7/1961 France 415/196 672,003 10/1963 Canada 415/200 Primary ExaminerHenry F. Raduazo Attorney-Robert L. Lehman [5 7 ABSTRACT A pump comprising a refractory body portion of oblate spheroidal configuration having apertures in the top and bottom thereof is provided with refractory covers for said apertures which covers are held securely in said apertures by upper and lower metal plates, respectively, the upper plate forming the base of a vertical housing for the pump impeller shaft and the lower plate being resiliently mounted for vertical movement relative to said upper plate to compensate for thermo-expansion and contraction of the pump elements.

7 Claims, 6 Drawing Figures PATENTED DEB 41975 SHEET 1 OF 3 PATENTEU DEE 4 5 SHEET 2 BF 3 PUMP FOR MOLTEN SALTS AND METALS This invention pertains to pumps of the centrifugal or rotary impeller type, and provides an improved such pump which is adapted for the pumping of molten salts and metals.

The pump is particularly adapted for the pumping in molten state of such corrosive media as the alkali and alkaline earth metals and salts thereof as well as aluminum and its salts, and of course is also applicable to the pumping in molten state of such less corrosive metals as lead, zinc and the like and salts thereof.

In U.S. Pats. Nos. 3,418,223 and 3,501,387, F. E. Love, and in a pending application Ser. No. 801,937 now U.S. Pat. No. 3,640,801 of said Love, there are described methods and apparatus for the continuous producton of magnesium metal from magnesium chloride, aluminum metal from alumina dissolved in aluminum fluoride and sodium fluoride and sodium metal from sodium chloride. In all such processes a salt of the metal in question in admixture with other such salts are circulated in a molten state through a series of electrolysis cells for recovery of the elemental metal which is circulated in a molten state to a refining cell, to storage or the like. As described in said patents and application, pumps are required for effecting such circulation of the molten salts and metals.

The present invention provides a pump adapted for such applications which is capable of rapidly pumping such molten media, at high discharge heads and over extended time intervals without deterioration or breakdown, and which we have found from extensive investigations is unique in these respects.

The pump of the invention is of simplified construction and assembly, constructed in part of metal alloys and in part of refractory materials of high room and elevated temperature corrosion resistance, the components of which are so assembled as to compensate for differences in thermal coefficients of expansion and contraction of the various components in heating and cooling, and such as resiliently to buttress, the refractressing of refractory components against tensile fracture has been ignored or inadequately disposed of.

The pump of the invention consists in its essentials of the following. A spirally vaned impeller is rotatively mounted within a housing, both of which are made of a refractory material which is highly resistant to corrosion and scoring by molten media of the character tory material components against rupture tending to be produced by fluid and other pressures exerted thereon in operation, and also in heating up the apparatus f0 use and subsequent cooling down.

Although numerous types of pumps have heretofore been devised for the pumping of molten metals and the like, all of those we have investigated, have proved deficient in one or more respects above noted, for the pumping of such corrosive media as above referred to. Some such previously known pumps, are constructed almost entirely of refractory materials, but such materials are brittle and of low tensile strength, and components thereof difficult to assemble by dowels and the like forming relatively weak joints, such as to produce rupture and rapid breakdown in use, and to necessitate relatively low pumping pressures and pressure heads due to tensile stresses induced therein. Others are constructed in part of refractory components and in part of metal components but the materials employed and the component assemblies are not adapted to withstand the rigors of rapidly pumping molten corrosive salts and metals at high pressures. Also in such known constructions the critical significance of compensating for differences in thermal coefficients of expansion between metal and refractory components and the butabove discussed. Suitable such refractories are described hereinafter. The main body of the housing is of roughly oblate spheroidal configuration, integral with a volute discharge outlet. The housing is axially apertured thru oppositely disposed oblate surface portions, respectively, for reception of a drive shaft secured to the impeller and to provide an inlet port for the molten material. A feature of the invention resides in mounting the housing under resilient compression between a pair of top and bottom metal retainer plates. The purposes of this construction are to maintain the housing under resilient compression with respect to fluid pressures exerted against the housing interior by the pumping action of the impeller, and also to compensate for differences in amounts of thermal expansion or contraction of the refractory housing versus the remaining metal component assembly of the pump both of which tend otherwise to place the housing under tension preductive of rupture. As is well known refractory materials, while weak in tensions are strong in compression. Hence by maintaining the housing at all times under resilient compression tensile stresses tending to produce rupture therein are eliminated. The shaft housing mounts on its upper end a coupling and drive assembly for the impeller shaft. A metal discharge conduit is connected to the volute discharge outlet of the impeller housing.

Having thus described the pump of the invention in general terms, reference will now be had for a more detailed description to the above and other features thereof to the accompanying drawings, wherein:

FIG. 1 is a view in side elevation and partly in section of the pump assembly of the invention.

FIGS. 2 and 3 are sectional views of FIG. 1 as taken at 2-2 and 3-3 thereof.

FIG. 4 is a plan view of the pump impeller, showing the impeller blades.

FIG. 5 is a perspective view of the impeller housing and appurtent components.

FIG. 6 is an exploded, perspective view of the essential components of the pump.

Referring to the drawings, the pump of the invention comprises an impeller 10 rotatively mounted within a housing generally designated by the numeral 11, and comprising components 13-16 inc. Referring to FIGS. 1 and 5, the main body of the housing 11, comprising an inner, refractory member 13, encased within an outer refractory casing 14 for purposes explained below, is of substantially oblate configuration, integral with a volute discharge outlet 17 for the molten media. It is axially apertured thru its upper and lower oblate portions, as at 18, 19, for reception, respectively, of a top cover 15 and an annular base member 16, which provides a suction inlet 17 for said molten media.

Referring to FIGS. 1, 4, 5 and 6, impeller 10, is rotatably mounted on a shaft adapter 21, and secured thereto by a hub cap 22, having a tapered shank of elliptical or octagonal cross section, as at 23, terminating in a threaded stud 24. The shank fits into a slot of corresponding taper and cross section of the impeller hub 25, and the stud is threaded into the lower end 27 of the shaft adapter for securing the same to the impeller. The shaft adapter'21 is in turn secured to the lower end of a shaft 28, rotatable within a tubular shaft housing or support column 29, the lower end of which is welded to a centrally apertured plate 30, bolted as at 31, to lugs as at 32, welded onto a top cover retainer plate 33, of the impeller housing. The support column 29 has welded to its upper end, a flanged member 34, on which is mounted a supporting structure 35, for a bearing 36 through which shaft 28 is journaled. Rotatably mounted atop structure 34, is a belt driven pulley 37, which is keyed to a shaft 38 journaled thru a bearing 39, and coupled, as at 40, to the impeller shaft 28.

Welded to the base of the support structure 37, is an upper support plate 41, which is drilled as at 42, 43, for slidable reception of a series of tension bars, as at 44, 45, the upper ends of which are resiliently supported on plate 41, by helical compression springs encircling the rods as at 46, 47, and interposed between the plate 41, and terminal lock nuts threaded onto the rods, as at 48, 49. The rods extend down thru holes in a bottom retainer plate 50, for the impeller housing 11, and terminate in lock nuts threaded thereon as at 51, 52. The rods are thus tensioned by the compression springs 46, 47 acting between their upper lock nuts and the upper plate 41, thereby to place the impeller housing under resilient compression between its upper and lower retainer plates 33 and 50, for purposes above explained and more in detail below. Thus by the action of the compression springs, a downward force is applied to plate 41 and transmitted thence via column 29 to the top housing retainer plate 33, while concurrently the tension rods apply an upward force to the bottom housing retainer plate 50.

The discharge outlet 17 for housing 11, is connected as shown in FIG. 1, to the lower end of an elbow pipe section 55, the upper end of which is connected through an expansion joint, as at 56, to a vertically disposed discharge pipe 57, which extends through an aperture in the upper support plate 41, and is vertically supported against lateral displacement by a collar 58, assembled on upstanding bolts, as at 59, threaded into the support plate 41.

Referring to FIGS. 4 and 6, the impeller 10, is a onepiece structure comprising a disc shaped backing portion 60, having a series of circumferentially spaced impeller blades projecting therefrom, as at 61, 62, which extend radially outward from the hub 26, in curved configuration.

Referring now to the materials of which the pump is constructed, the impeller 20 and the impeller housing components 13, and 16 are made of a refractory material, resistant to scoring and corrosion by molten metals or salts of the character above discussed. The preferred refractory is silicon carbide bonded with silicon about 1 percent manganese, up to about 2 percent silicon, about 1.75-4.15 percent columbium or columbium and tantalum, and up to about 0.2 percent carbon. Preferred alloys are those designated by the trade names lnconel 600, 611 and 625 of the following compositions:

Weight Element lnconel 600 lnconel 611 lnconel 625 Cr 14-17 14-17 20-23 Fe 6-8 8-11 5 max. Mn 1.0 max. 1.5 max. 0.5 max. Si 0.75 max. 2 max. 0.5 max. C 0.1 max. 0.2 max. 0.1 max. Cb/Ta 1.75-2.75 1-3 3.65-4.15 Ni 72 rnin.Ba1. Balance Balance The preferred alloy for purposes of this invention is Inconel 611.

Reverting to the drawings, the pump components made of these high nickel alloys comprise the top and bottom retainer plates 33 and 50, the impeller hub 22, the impeller shaft adapter and shaft 21, 28, the shaft housing 29, flange 30 and appurtent components, the tension bars 44, 45, the elbow discharge coupling 55, the expansion joint coupling 56 and discharge pipe 57.

The outer casing 14 for the housing member 13, consists of a laminated build-up of about 3/4-1 inch thick composed of layers of fiber glass cloth embedded in and bonded by a high aluminum cement. The casing 14 as thus constructed serves as a heat sink to minimize thermal shock of the inner refractory casing member 13.

We claim 1. A centrifugal pump adapted for pumping molten salts and metals comprising:'a spirally vaned impellerrotatively mounted within a substantially oblate housing having a volute outlet connected to a conduit for discharge of said molten media, said housing being axially apertured on its opposite oblate surfaces for reception of a drive shaft keyed to said impeller and to provide an entry port for said molten media, respectively, said impeller and housing being composed of a refractory material highly resistant to corrosion and scoring by said molten media, said housing being mounted between a rigid structure engaging one oblate surface thereof and a supporting structure engaging the opposite oblate surface thereof, said rigid structure comprising a tubular member housing said shaft and having one flanged end bearing against one oblate surface of said housing and an opposite flanged end mounting coupling means and a drive member for said shaft,'and also mounting a plate extending radially from said shaft beyond the confines of said housing, said plate being apertured for reception of rods slidably disposed therein, said rods being resiliently suspended on said plate by compression springs, and extending to and being secured to said supporting structure for resiliently compressing said housing between said rigid and said supporting structures.

2. A pump according to claim 1 wherein said rigid and supporting structures, said rods and said conduit are composed of nickel base alloy metal.

3. A pump according to claim 2 wherein said impeller and housing are composed of refractory material selected from the group consisting of aluminum oxide,

silicon oxide, silicon-oxy-nitride, tri-silicon nitride, silicon carbide and bonded combinations thereof.

4. A pump according to claim 3 wherein said impeller and housing of composed of silicon carbide bonded with silicon nitride.

5. A pump according to claim 3 wherein said refractory housing is incased within a thermally insulating and shock resistant casing composed of fiber glass and refractory material bonded thereto.

6. A pump according to claim 1 wherein said refractory oblate housing includes in combination therewith, a refractory cover plate fitted into one axial aperture thereof, said cover plate forming the bearing for said one flanged end of said tubular member and being apertured for reception of said drive shaft, and the oppomaintain said housing under compression. 

1. A centrifugal pump adapted for pumping molten salts and metals comprising: a spirally vaned impeller rotatively mounted within a substantially oblate housing having a volute outlet connected to a conduit for discharge of said molten media, said housing being axially apertured on its opposite oblate surfaces for reception of a drive shaft keyed to said impeller and to provide an entry port for said molten media, respectively, said impeller and housing being composed of a refractory material highly resistant to corrosion and scoring by said molten media, said housing being mounted between a rigid structure engaging one oblate surface thereof and a supporting structure engaging the opposite oblate surface thereof, said rigid structure comprising a tubular member housing said shaft and having one flanged end bearing against one oblate surface of said housing and an opposite flanged end mounting coupling means and a drive member for said shaft, and also mounting a plate extending radially from said shaft beyond the confines of said housing, said plate being apertured for reception of rods slidably disposed therein, said rods being resiliently suspended on said plate by compression springs, and extending to and being secured to said supporting structure for resiliently compressing said housing between said rigid and said supporting structures.
 2. A pump according to claim 1 wherein said rigid and supporting structures, said rods and said conduit are composed of nickel base alloy metal.
 3. A pump according to claim 2 wherein said impeller and housing are composed of refractory material selected from the group consisting of aluminum oxide, silicon oxide, silicon-oxy-nitride, tri-silicon nitride, silicon carbide and bonded combinations thereof.
 4. A pump according to claim 3 wherein said impeller and housing of composed of silicon carbide bonded with silicon nitride.
 5. A pump according to claim 3 wherein said refractory housing is incased within a thermally insulating and shock resistant casing composed of fiber glass and refractory material bonded thereto.
 6. A pump according to claim 1 wherein said refractory oblate housing includes in combination therewith, a refractory cover plate fitted into one axial aperture thereof, said cover plate forming the bearing for said one flanged end of said tubular member and being apertured for reception of said drive shaft, and the opposite axial aperture of said oblate housing includes an annular refractory member fitting therein to provide a refractory inlet for said molten mEdia.
 7. A pump according to claim 6 wherein said rigid and support structures and rods are made of nickel base alloy metal having a different coefficient of thermal expansion from that of the refractory of said housing, whereby said compression springs function to compensate for differences in amounts of thermal expansion and contraction of said housing and metal members produced by temperature variations, thereby to maintain said housing under compression. 